Difference Between Nucleus and Nucleoid

Nucleus vs Nucleoid

Within every living cell, there is a region that controls the cell functions and inheritance. For eukaryotes, it is called “Nucleus” while, for prokaryotes, it is called “Nucleoid”. Either nucleus or nucleoid, both contain genetic information that is encoded in the genetic material. Usually the genetic material is DNA in both cases. Though the function of these two is nearly similar, their structure and organization can be differed in many ways.


Nucleus is the largest and most important cellular organelle in an eukaryotic cell. Usually it is spherical or oval in shape and is placed in the centre of the cell. Nucleus generally consists of the nuclear membrane, nucleoplasm, chromatin material, and the nucleolus. Eukaryotic cells have double layered nuclear membrane which separates the nucleus from the cytoplasm. The nuclear pores allow the transfer of nuclear material from nucleus to the cytoplasm. Nucleoplasm is a granular dense fluid. Chromatin and nucleolus are suspended in this homogenous fluid. Chromatin mainly consists of long, coiled DNA strands which are vital in transmitting genetic information from one generation to another. Nucleolus is a spherical structure found inside the nucleus, made up of RNA and proteins. The nucleus regulates all metabolic reactions of the cell and regulates the cell cycle while contributing to transmit the genetic material from one generation to another.


Nucleoid is mainly found in Prokaryotes such as bacteria and blue-green algae. It is an undefined nuclear region containing only nucleic acids. Generally it contains single circular chromosome, which stores genetic information of prokaryotes. There is no nuclear membrane and other organized nuclear regions in nucleoid when compared to nucleus. Due to lack of surrounding membranes, this is not separated from the remainder of the prokaryotic cytoplasm.

What is the difference between Nucleus and Nucleoid?

• Nucleus is the structure where Eukaryotes store their genetic material while nucleoid is the place where Prokaryotes store their genetic material.

• Nucleus is large and well organized, whereas nucleoid is small and poorly organized.

• Nucleus is surrounded by a double layered membrane called “nuclear membrane” and separates from other cell organelles. Such membrane cannot be found in nucleoid.

• Nucleus contains many chromosomes while nucleoid generally has only one circular DNA molecule.

• Nucleolus and nucloeplasm are present inside the nucleus, whereas they are absent in nucleiod.